1. Field of the Invention
The present invention pertains to fluid-pressure operable mechanical systems. More particularly, the present invention relates to piston-and-cylinder assemblies, and may be used with advantage, for example, in applications where relatively extended stroke length is required in combination with limited distance storage requirements.
2. Description of Prior Art
Fluid pressure piston-cylinder assemblies are known for use in maneuvering various forms of equipment, and particularly for manipulating mobile apparatus used in working on wells. Thus, for example, masts may be raised or lowered on drilling rigs by way of fluid pressure cylinder assemblies.
Coiled tubing systems for working on wells are known to utilize piston-cylinder assemblies for elevating the injector head of such a system to selected positions along a mast. Such well working systems are discussed in detail in copending U.S. patent application Ser. No. 913,118 filed June 6, 1978, assigned to the same assignee as the present case, wherein improvements in coiled tubing systems are disclosed.
In prior art coiled tubing systems, a single piston-cylinder assembly is mounted along each leg of a two legged mast. The piston rods extend down the mast to support the injector head. By appropriate control of the fluid pressure applied to the cylinders, the injector head may be selectively raised or lowered along the mast.
Such masts and associated equipment may be mounted on a truck or barge. In the case of such mobile systems, the mast may be folded, for example, to achieve an acceptable road clearance profile for transportation purposes. Then, the injector head is either tilted with the folded portion of the mast as in the prior art, or is first lowered below the position of the mast hinge assemblies as disclosed in the aforementioned copending application. However, in order to provide the increased range of movement along the mast required for the injector head that may be so lowered below the mast hinge point, conventional piston-cylinder assemblies would have to be increased in both cylinder and piston rod length.